U.S. patent application number 16/280518 was filed with the patent office on 2020-08-20 for internal combustion engines having super knock mitigation controls and methods for their operation.
This patent application is currently assigned to King Abdullah University of Science and Technology. The applicant listed for this patent is King Abdullah University of Science and Technology Saudi Arabian Oil Company. Invention is credited to Mohammed Jaasim Mubarak Ali, Robert W. Dibble, Hong G. Im, Gautam T. Kalghatgi, Kai J. Morganti, Vallinayagam Raman, Eshan Singh, Vedharaj Sivasankaralingam.
Application Number | 20200263651 16/280518 |
Document ID | 20200263651 / US20200263651 |
Family ID | 1000003941686 |
Filed Date | 2020-08-20 |
Patent Application | download [pdf] |
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United States Patent
Application |
20200263651 |
Kind Code |
A1 |
Singh; Eshan ; et
al. |
August 20, 2020 |
INTERNAL COMBUSTION ENGINES HAVING SUPER KNOCK MITIGATION CONTROLS
AND METHODS FOR THEIR OPERATION
Abstract
According to one or more embodiments presently described, a
method of operating an internal combustion engine that includes
injecting fuel into a combustion chamber to form an air-fuel
mixture, where the combustion chamber includes a cylinder head,
cylinder sidewalls, and a piston that reciprocates within the
cylinder sidewalls. The method may also include detecting
pre-ignition of the air-fuel mixture during a detected intake or
compression stroke of the piston, determining that a super knock
condition could occur, and mitigating formation of a super knock
condition by deploying a super knock countermeasure within the
detected compression stroke.
Inventors: |
Singh; Eshan; (Thuwal,
SA) ; Sivasankaralingam; Vedharaj; (Thuwal, SA)
; Raman; Vallinayagam; (Thuwal, SA) ; Ali;
Mohammed Jaasim Mubarak; (Thuwal, SA) ; Im; Hong
G.; (Thuwal, SA) ; Morganti; Kai J.; (Dhahran,
SA) ; Kalghatgi; Gautam T.; (Dhahran, SA) ;
Dibble; Robert W.; (Thuwal, SA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
King Abdullah University of Science and Technology
Saudi Arabian Oil Company |
Thuwal
Dhahran |
|
SA
SA |
|
|
Assignee: |
King Abdullah University of Science
and Technology
Thuwal
SA
Saudi Arabian Oil Company
Dhahran
SA
|
Family ID: |
1000003941686 |
Appl. No.: |
16/280518 |
Filed: |
February 20, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F02P 11/02 20130101;
F02D 35/021 20130101; G01L 23/22 20130101; F02P 5/04 20130101; F02D
35/027 20130101 |
International
Class: |
F02P 5/04 20060101
F02P005/04; F02D 35/02 20060101 F02D035/02; F02P 11/02 20060101
F02P011/02 |
Claims
1. A method of operating an internal combustion engine, the method
comprising: injecting fuel into a combustion chamber to form an
air-fuel mixture, the combustion chamber comprising a cylinder
head, cylinder sidewalls, and a piston that reciprocates within the
cylinder sidewalls; detecting pre-ignition of the air-fuel mixture
during a detected intake or compression stroke of the piston;
determining that the internal combustion engine is operating at a
condition at which a super knock condition could occur; and
mitigating formation of a super knock condition by deploying a
super knock countermeasure within the detected compression
stroke.
2. The method of claim 1, wherein the super knock countermeasure
comprises advancing spark timing.
3. The method of claim 2, wherein spark timing is advanced to a set
point at which the air-fuel mixture is burned prior to the cylinder
reaching top dead center.
4. The method of claim 1, wherein the super knock countermeasure
comprises opening an exhaust valve to pass burned and unburned
air-fuel mixture from within the combustion chamber to outside of
the combustion chamber.
5. The method of claim 4, wherein the super knock countermeasure
further comprises interrupting a spark plug that is positioned
within the combustion chamber from normal discharging during the
detected compression stroke.
6. The method of claim 1, wherein the super knock countermeasure
comprises injecting additional fuel into the combustion
chamber.
7. The method of claim 1, wherein the detection of pre-ignition is
sensed by an ion sensor.
8. The method of claim 7, wherein the ion sensor comprises an
alternating current phase lock loop circuit or a band pass filter
circuit.
9. The method of claim 7, wherein the ion sensor comprises a spark
plug comprising an electrode, the electrode positioned within the
combustion chamber.
10. The method of claim 7, wherein the determination that the super
knock condition could occur comprises sensing ion currents in the
combustion chamber at a crank angle prior to a spark plug being
discharged.
11. The method of claim 10, wherein the determination that the
super knock condition could occur comprises evaluating an engine
rotational speed and an engine load.
12. The method of claim 1, wherein the detection of pre-ignition is
sensed by a pressure sensor that is positioned to sense pressure
within the combustion chamber.
13. The method of claim 1, wherein the detection of pre-ignition is
sensed by one or more of a crank angle sensor, a crank speed
sensor, or crank accelerometer that detects a change in rotational
acceleration of a rotating engine component that is coupled to the
piston.
14. The method of claim 13, wherein the rotating engine component
comprises a crankshaft that is coupled to the piston by a
connecting rod.
15. An internal combustion engine, comprising: an engine cylinder
comprising a cylinder head and cylinder sidewalls; a piston that
reciprocates within the engine cylinder, wherein the piston, the
cylinder head, and the cylinder sidewalls at least partially define
a combustion chamber; a spark plug that is positioned to extend
into the combustion chamber; an ion sensor that is positioned to
sample conditions within the combustion chamber; and an engine
control module in electronic communication with the ion sensor and
the spark plug, the engine control module comprising a processor
and a memory storing a computer readable instruction set that, when
executed by the processor: evaluates at what crank angle in a
detected intake or compression stroke the ion sensor senses ion
current in the combustion chamber; and deploys a super knock
countermeasure within the detected compression stroke when ion
currents are detected prior to a prior to the spark plug being
discharged.
16. The internal combustion engine of claim 15, wherein the engine
control module deploys the super knock countermeasure of early
discharging the spark plug during the detected compression stroke
before the piston reaches top dead center.
17. The internal combustion engine of claim 16, wherein the engine
control module discharges the spark plug during the detected
compression stroke to burn all that remains of an air-fuel mixture
that is present in the combustion chamber before the piston reaches
top dead center.
18. The internal combustion engine of claim 15, further comprising:
an exhaust valve that selectively closes the combustion chamber;
and a lift mechanism coupled to the exhaust valve, wherein the lift
mechanism is in electronic communication with the engine control
module.
19. The internal combustion engine of claim 15, wherein the ion
sensor comprises of a direct current circuit or an alternating
current phase lock loop circuit or a band pass filter circuit.
20. The internal combustion engine of claim 15, further comprising
a compressor positioned to pressurize an intake manifold that is in
selective fluid communication with the combustion chamber.
Description
BACKGROUND
Field
[0001] The present disclosure relates to internal combustion
engines and, more specifically, to internal combustion engines
having super knock mitigation controls.
Technical Background
[0002] Forced induction internal combustion engines include
superchargers or turbochargers that pressurize an intake manifold
to increase the mass of air that enters a combustion chamber during
an intake stroke. At certain operating conditions, such engines are
prone to develop super knock, which is a condition in which
air-fuel mixture in the combustion chamber pre-ignites, which leads
to high cylinder pressures that may damage engine components.
BRIEF SUMMARY
[0003] Accordingly, internal combustion engines that include super
knock mitigation controls may be desired. As disclosed herein,
internal combustion engines may include super knock mitigation
controls that detect when conditions of super knock are occurring
and deploy super knock countermeasures to reduce or eliminate the
formation of the super knock conditions in the detected intake or
compression stroke. The engine control modules of the internal
combustion engines may sense the presence of conditions leading to
super knock, for example, pre-ignition of the air-fuel mixture,
accelerated pressure rise in the combustion chamber, or an
anomalous decrease of rotational speed of the engine crankshaft
prior to discharge of the spark plug. Through early detection of
these conditions, countermeasures can be deployed within the
compression stroke to mitigate or eliminate the formation of super
knock conditions during the detected compression stroke.
[0004] Example of such super knock countermeasures may include
injection of additional fuel into the combustion chamber,
advancement of the spark plug discharge to combust, earlier, the
air-fuel mixture, early exhausting of the unburned or partially
burned air-fuel mixture through the exhaust valve, or combinations
thereof. By deploying such countermeasures, super knock conditions,
including the high pressures that are associated with damaging
engine components, can be avoided or minimized, thereby preserving
the engine components.
[0005] According to one or more embodiments, a method of operating
an internal combustion engine includes injecting fuel into a
combustion chamber to form an air-fuel mixture, the combustion
chamber comprising a cylinder head, cylinder sidewalls, and a
piston that reciprocates within the cylinder sidewalls. The method
further includes detecting pre-ignition of the air-fuel mixture
during an intake or compression stroke of the piston, determining
that the internal combustion engine is operating at a condition at
which a super knock condition could occur, and mitigate formation
of a super knock condition by deploying a super knock
countermeasure within the detected compression stroke.
[0006] According to one or more additional embodiments, an internal
combustion engine includes an engine cylinder comprising a cylinder
head and cylinder sidewalls, a piston that reciprocates within the
engine cylinder, where the piston, the cylinder head, and the
cylinder sidewalls at least partially define a combustion chamber,
and an ion sensor that is positioned to sample conditions within
the combustion chamber. The internal combustion engine also
includes an engine control module in electronic communication with
the ion sensor, where the engine control module includes a
processor and a memory storing a computer readable instruction set.
When executed by the processor, the engine control module evaluates
at what crank angle in a detected compression stroke the ion sensor
senses ion currents in the combustion chamber and deploys a super
knock countermeasure within the detected compression stroke when
ion currents are detected prior to a spark plug being
discharged.
[0007] Additional features and advantages of the technology
disclosed in this disclosure will be set forth in the detailed
description which follows, and in part will be readily apparent to
those skilled in the art from the description or recognized by
practicing the technology as described in this disclosure,
including the detailed description which follows, the claims, as
well as the appended drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The following detailed description of specific embodiments
of the present disclosure can be best understood when read in
conjunction with the following drawings, where like structure is
indicated with like reference numerals and in which:
[0009] FIG. 1 schematically depicts a cross-sectional view of a
portion of an engine cylinder of an internal combustion engine,
according to one or more embodiments described herein;
[0010] FIG. 2 schematically depicts a partial cross-sectional view
of a portion of a cylinder of an internal combustion engine,
according to one or more embodiments described herein;
[0011] FIG. 3 schematically depicts an alternating current AC band
pass filter circuit for detection of AC or DC ion current,
according to one or more embodiments described herein; and
[0012] FIG. 4 schematically depicts a partial cross-sectional view
of a portion of a cylinder of an internal combustion engine,
according to one or more embodiments described herein.
[0013] Reference will now be made in greater detail to various
embodiments, some embodiments of which are illustrated in the
accompanying drawings. Whenever possible, the same reference
numerals will be used throughout the drawings to refer to the same
or similar parts.
DETAILED DESCRIPTION
[0014] Described herein are one or more embodiments of internal
combustion engines having super knock mitigation controls and
methods for the operation thereof. The internal combustion engines
may be capable of detecting pre-ignition of the air-fuel mixture
during the intake stroke or compression stroke of the piston. The
engines may also include engine control modules that determine the
likelihood of the occurrence of a super knock condition and, upon
detection of pre-ignition of the air-fuel mixture at conditions
having a high likelihood of the occurrence of super knock
conditions, the engine control module may deploy a super knock
countermeasure within the detected intake or compression stroke to
interrupt the formation of a super knock condition.
[0015] As described herein, a super knock condition in a
spark-ignition internal combustion engine refers to an occurrence
of irregular combustion of the air-fuel mixture in the combustion
chamber in which combustion is started by pre-ignition.
"Pre-ignition" represents the combustion of the fuel-air mixture
triggered by a "`hot-spot," other than the spark, prior to the
spark timing. However, depending on pre-ignition timing and
pre-ignition location within the combustion chamber, pre-ignition
may cause subsequent different combustion phenomena, including
non-knocking combustion. Super knock often occurs under low-speed
and high-load engine operating conditions. Super knock conditions
appear to occur sporadically when evaluating the engine
cycle-to-cycle, and therefore accurate prediction of whether super
knock conditions will occur may not be directly correlated to
engine operating conditions alone. Determining that such engine
operating conditions are present may aid in determining the
likelihood of a super knock condition.
[0016] Super knock is distinguished from conventional engine knock,
which is due to auto-ignition of the end-gas of the air-fuel
mixture before the spark plug-initiated flame propagation consumes
the end gas in the combustion chamber.
[0017] Referring to FIG. 1, a schematic illustration of a portion
of an internal combustion engine 100 is depicted. In particular,
FIG. 1 depicts a single engine cylinder 110 of an internal
combustion engine 100. However, as is understood by those having
skill in the art, an internal combustion engine 100 may comprise
numerous engine cylinders, such as engine cylinder 110, which may
be arranged in a variety of configurations along the length of one
or more crank shafts, such as crank shaft 180 depicted in FIG.
1.
[0018] The internal combustion engine 100 may comprise at least an
engine cylinder 110, an intake port 171, an exhaust port 173, and a
piston 120. The intake port 171 is regulated by an intake valve 172
that is positioned to selectively open and close the intake port
171 that connects to the engine cylinder 110 with an intake
manifold 140. Similarly, the exhaust port 173 is regulated by an
exhaust valve 174 that is positioned to selectively open and close
the exhaust port 173 that connects the engine cylinder 110 to an
exhaust manifold 150.
[0019] The volume defined on the top and sides by the engine
cylinder 110 and on the bottom by the piston 120 is referred to as
the combustion chamber 122. The intake port 171 and the exhaust
port 173 allow air, air-fuel mixture, and/or combustion products to
enter and exit the combustion chamber 122 at various times
throughout the engine cycle. A spark plug 118 includes an electrode
that is positioned at the combustion chamber 122 to provide
combustion initiation in timed electrical bursts. In some
embodiments, the spark plug 118 may be positioned at or near the
center of the combustion chamber 122 (for example, at or near the
radial center with respect to the walls of the cylindrical-shaped
engine cylinder 110).
[0020] In some embodiments, the intake valve 172 and/or the exhaust
valve 174 are connected to one or more cams or camshafts (not
depicted in FIG. 1) which may serve to selectively open and close
the intake valve 172 and/or the exhaust valve 174, which thereby
maintain the selective opening and closing of the respective intake
port 171 and exhaust port 173 in time with the engine operation.
The piston 120 may be coupled to a crank shaft 180 by a connecting
rod 182. The engine cylinder 110 may comprise a cylinder head 114
and cylinder sidewalls 112. The intake port 171 and the exhaust
port 173 may be positioned on the cylinder head 114. Additionally,
a fuel injector 116 and spark plug 118 may be positioned in the
cylinder head 114 and extend into the combustion chamber 122 such
that the fuel injector 116 and the spark plug 118 can act on the
air and/or air-fuel mixture that is present within the combustion
chamber 122. The spark plug 118 may be electronically coupled to an
ignition system 119 that electrically discharges via the spark plug
118.
[0021] It should be understood that while FIG. 1 depicts a direct
injection configuration (that is, the fuel enters the combustion
chamber 122 directly by fuel injector 116), a port injection scheme
(sometimes referred to as indirect injection) may be suitable in
other embodiments, where fuel is injected into the intake port 171
and is subsequently passed into the combustion chamber 122. As
such, the "injecting" (i.e., the "passing") of fuel into the
combustion chamber 122 may comprise direct injection, port
injection (indirect injection), or both.
[0022] The internal combustion engine 100 may operate by repeated
combustion of an air-fuel mixture that is present within the
combustion chamber 122 during a compression and an expansion
stroke. The combustion of the air-fuel mixture further pressurizes
the combustion chamber 122, which causes the piston 120 to
translate away from the cylinder head 114. The translation of the
piston 120 rotates the crank shaft 180. As the piston 120
translates away from the cylinder head 114, the high pressure in
the combustion chamber 122 from the combustion of the air-fuel
mixture is directed into the rotation of the crank shaft 180. The
crank shaft 180 may rotate through a top dead center position
(corresponding to the closest position of the piston 120 relative
to the cylinder head 114) and a bottom dead center position
(corresponding to the furthest position of the piston 120 relative
to the cylinder head 114). In one or more embodiments, the internal
combustion engine 100 may operate as a four stroke engine, although
other engine configurations are contemplated. In such an
embodiment, intake, compression, power, and exhaust strokes cycle
in a regular and sequential manner. In the intake stroke, the
piston moves downward and air and/or fuel may enter the combustion
chamber 122 through the intake port 171. In the compression stroke,
the air and/or fuel are compressed as the piston 120 moves toward
the cylinder head 114. Fuel is also injected into the combustion
chamber 122 during the intake stroke or early in the compression
stroke. In the power stroke, the piston is forced away from the
cylinder head 114 by combusted air-fuel mixture, which is now at an
elevated temperature and pressure due to the combustion of the
air-fuel mixture near or at TDC. In the exhaust stroke, the piston
120 moves toward the cylinder head 114 to direct exhaust gases
(products of the combustion reaction) out of the combustion chamber
122 through the open exhaust port 173.
[0023] The internal combustion engine 100 also includes a
compressor 90 that is positioned proximate to the intake manifold
140. The compressor 90 increases the pressure of the air that is in
the intake manifold 140, so that a larger mass of air can be
directed into the combustion chamber 122 during an intake stroke.
The compressor 90 may be coupled to a turbine (not shown) that is
positioned within an exhaust manifold 150. The turbine extracts
energy from the combustion products and uses that energy to
pressurize air directed into the intake manifold 140. Such a
compressor 90 and turbine system is referred to as a
"turbocharger." In other embodiments, the compressor 90 may be
coupled to rotating hardware of the internal combustion engine 100,
for example the crank shaft 180. Such a rotationally coupled
compressor 90 is referred to as a "supercharger."
[0024] The internal combustion engine 100 also includes an engine
control module 80. The engine control module 80 may include a
processor 82 and a memory 84 storing a computer readable
instruction set and look-up tables. The engine control module 80 is
in electronic communication with various components of the internal
combustion engine 100, including the fuel injector 116, the
ignition system 119 that is in electronic communication with the
spark plug 118, various engine sensors, such as a throttle position
sensor (not shown), an intake manifold pressure and temperature
sensor (not shown), and a crank angle sensor 181 that detects the
angular orientation of the crankshaft 180 throughout its range of
rotation. The engine control module 80 may evaluate the various
engine sensors to determine the operational condition of the engine
and power demand from the operator. The engine control module 80
may modify the timing and quantity of fuel delivered to the
combustion chamber 122 by controlling the fuel injector 116 and may
also modify the timing of the discharge of the spark plug 118. The
engine control module 80 is programmed with a fuel schedule and a
spark timing schedule, which allows the internal combustion engine
100 to be operated according to pre-defined characteristics that
satisfies power delivery, fuel consumption, and emissions
targets.
[0025] In some embodiments, the internal combustion engine 100 may
include an ion sensor 190 that is positioned to sense the presence
of ions in the combustion chamber 122. In the depicted embodiment,
the ion sensor 190 is incorporated into the spark plug 118. Without
being bound by theory, combustion of an air-fuel mixture releases
ions within the combustion chamber 122. These ions can create an
ion cloud in the combustion chamber 122. An ion cloud generally
refers to an area of increased concentration of ions, which may
fill or partially fill the combustion chamber 122. An ion sensor
190 can detect the ion cloud by inducing an ion current via an
applied voltage between electrodes. When the ion current is
detected in the compression cycle prior to discharge of the spark
plug 118, it can be assumed that the detected ion current in the
combustion chamber 122 was caused by pre-ignition of the air-fuel
mixture. Therefore, early detection of pre-ignition in the
combustion chamber 122 may allow for countermeasures to be deployed
to mitigate the subsequent formation of super knock conditions.
[0026] The ion sensor 190 is in electronic communication with the
engine control module 80. In the embodiment depicted in FIG. 1, the
ion sensor 190 is incorporated into the spark plug 118, such that
the spark plug 118 can be used to detect the presence of ion
currents in the combustion chamber 122. The spark plug 118 includes
an electrode 117 that can be used to detect the presence of an ion
current in the combustion chamber 122. Referring to FIG. 2, in some
embodiments, the ion sensor 190 may be a stand-alone sensor that is
independent from the spark plug 118 and is positioned to sample
within the combustion chamber 122.
[0027] Ions generated by the combustion of the air-fuel mixture in
the combustion chamber 122 may be detected by the ion sensor 190
that may fluctuate in a predetermined frequency band, for example
from about 8 kHz to about 13 kHz. Detecting variations in the ion
current within this frequency band may correspond to a pre-ignition
event of the air-fuel mixture. The frequency bands at which the ion
current tends to fluctuate may vary based on engine hardware and/or
engine load conditions. In some embodiments, the frequency band may
be targeted based on known conditions at which there is an
increased likelihood of super knock conditions forming.
[0028] According to one more embodiments, the ion sensor 190 may be
a direct current sensor. In one or more alternative embodiments,
the ion sensor 190 may be an alternating current sensor. In
embodiments where an alternating current sensor is utilized, a band
pass filter circuit or a phase lock loop detection circuit may be
incorporated. For example, now referring now to FIG. 3, the ion
sensor 190 may be coupled to a band pass filter circuit 192. The
band pass filter circuit 192, as depicted, includes a signal
generator 194, an analogue band pass filter 196, an integration
half or full wave rectifier 197, and a threshold detector 199 such
as a pulse delay generator trigger. The integration half or full
wave rectifier 197 may include an integration capacitor and
resistor combination. In one embodiment, the signal generator may
operate at 10 kHz at a voltage of 20-110 volts measured
peak-to-peak. The analogue band pass filter 196 may operate at 10
kHz. The band pass filter circuit 192 may include a first resister
195 at 0.5 Mega Ohms and a second resister 198 at 1.0 Mega Ohms.
The band pass filter circuit 192 detects when there is an ion
current signal that is measured to the ion sensor 190. The band
pass filter circuit 192 may also filter noise from the input signal
to reduce the likelihood of false-positives of detection of an ion
current. The band pass filter circuit 192 may also allow for
detection of the ion current at the detected frequency to allow for
detection of nascent ion current quickly after development of a
pre-ignition spot in the air-fuel mixture. In additional
embodiments, a phase lock loop detection circuit may be utilized
which operates on the principles of phase lock loop control.
[0029] Referring again to FIG. 1, in operation, the ion sensor 190
may quickly detect the presence or emerging presence of an ion
current signal that corresponds to the nascent existence of ions in
the combustion chamber 122. Because the ion sensor 190 is quick to
detect such an ion creation, the engine control module 80 may
deploy countermeasures within the detected compression stroke in
which the ions are detected. By being able to rapidly deploy such
countermeasures (e.g., within the same engine stroke), the engine
control module 80 can mitigate the formation of super knock
conditions in the combustion chamber 122 during the detected
compression stroke. In some embodiments, the super knock
countermeasure is deployed well before the piston reaches top dead
center in the compression stroke. This rapid deployment allows for
real-time correction of the conditions which may cause super
knock.
[0030] The presence of ions in the combustion chamber 122 may
indicate the initiation of combustion in the combustion chamber
122. The presence of an ion current in the combustion chamber 122
indicates the presence of ions. The presence of ions prior to
discharging of the spark plug 118, therefore, may indicate
pre-ignition of the air-fuel mixture. Early detection of an ion
current in the combustion chamber 122, therefore, can be used to
determine the likelihood of a super knock condition being present
in the combustion chamber 122. For example, if the internal
combustion engine 100 is operating at a condition at which super
knock could occur, or is more likely to occur (e.g., low speed high
load conditions), the detection of ions in the combustion chamber
122 prior to discharge of the spark plug 118 may indicate that a
super knock condition is likely. In one or more embodiments, the
conditions in which super knock is could occur, or is more likely
to occur may include engine speed of less than 3000 rotations per
minute and at least 17 bar load. Further, in some embodiments, the
presence of the ions may be detected over a number of crank angles
while the piston is moving in the compression stroke, which may
further indicate that super knock conditions are possible or
likely. The engine control module 80 of the internal combustion
engine 100, therefore, may initiate a super knock countermeasure
during the measured compression stroke to mitigate the formation of
super knock conditions in the combustion chamber 122.
[0031] In some embodiments, the amount of ion current detected in
the combustion chamber 122 also corresponds to the amount of fuel
that is consumed in the combustion chamber 122. Accordingly, the
engine control module 80 can determine from the amount of fuel
consumed over a number of crank degrees to determine with increased
precision whether the air-fuel mixture is being consumed in an
amount corresponding to a higher likelihood that a super knock
condition will occur.
[0032] Referring again to FIG. 2, in some embodiments, the internal
combustion engine 100 may include a pressure sensor 290 that is
positioned to sense the pressure in the combustion chamber 122. In
one embodiment, the pressure sensor 290 is coupled to the cylinder
head 114 of the internal combustion engine 100, and a portion of
the pressure sensor 290 may be positioned to extend into the
combustion chamber 122. The pressure sensor 290 is in electronic
communication with the engine control module 80. The pressure
sensor 290 evaluates the pressure within the combustion chamber
122. The engine control module 80 or another processing computer
can compare the pressures measured in the combustion chamber 122 by
the pressure sensor 290 at various crank angles with a nominal
pressure profile for each compression stroke. By comparing the
measured pressures during each compression stroke, the engine
control module 80 can determine if the instantaneous measured
compression stroke is deviating from the nominal pressure profile.
If the pressure profile for the measured compression stroke exceeds
the pressure in the nominal pressure profile, it can be assumed
that the pressure in the combustion chamber 122 is rising more
quickly than in the nominal profile due to pre-ignition of the
air-fuel mixture. In such cycles, the engine control module 80 may
initiate a super knock countermeasure during the measured
compression stroke to mitigate the formation of super knock
conditions in the combustion chamber 122.
[0033] Referring again to FIG. 1, the instantaneous rotational
speed of the crank shaft 180 may slow during a compression stroke
in which pre-ignition of the air-fuel mixture is occurring. The
pressures inside the combustion chamber 122 may increase with
pre-ignition of the air-fuel mixture, which may increase the
resistance of the piston 120 to move toward the cylinder head 114.
The increased pressure in the combustion chamber 122, therefore,
may slow the rotational speed of the crank shaft 180. In some
embodiments, a decrease in the rotational speed of the crank shaft
180 may be measured by sensors that evaluate the position, speed,
or acceleration of the crank shaft 180. Such sensors may include,
for example, the crank angle sensor 181, a crank speed sensor (not
shown), or a crank accelerometer 183. The sensors, for example, the
crank angle sensor 181 and the crank accelerometer 183, are in
electronic communication with the engine control module 80. The
engine control module 80 or another processing computer can
determine if the crank shaft 180 is exhibiting an instantaneous
decrease in rotational velocity during the compression stroke
within one of the internal combustion engine's 100 combustion
chambers 122. If such a decrease in rotational velocity of the
crank shaft 180 is detected, the engine control module 80 may
initiate a super knock countermeasure during the measured
compression stroke to mitigate the formation of super knock
conditions in the combustion chamber 122.
[0034] As highlighted hereinabove, a super knock condition is
possible or likely to occur when the air-fuel mixture that is
present in the combustion chamber 122 pre-ignites prior to
initiation of a flame front caused by discharge of the spark plug
118 and typically at low speed high power engine conditions. It
should be appreciated that a number of factors play into the
probability that super knock will occur, and that the presently
disclosed systems and methods may be utilized to identify the
possibility of or the relatively high probability of superknock
occurring and deploying preventative measures. For example, the
preventative measures may be employed when superknock has a 1%, 5%,
10%, 25%, or even 50% chance of occurring. Embodiments of the
internal combustion engine 100 according to the present disclosure
are capable of deploying super knock countermeasures during the
compression stroke of the internal combustion engine 100 in which
pre-ignition of the air-fuel mixture is detected. Deploying such
super knock countermeasures within the detected compression stroke
allows the internal combustion engine to mitigate the formation of
super knock conditions, which may result in lower cylinder
pressures being exhibited in the combustion chamber 122 than when
super knock conditions are present. Further, because the super
knock conditions appear sporadically, the super knock
countermeasures can be deployed only in compression strokes that
correspond to a high likelihood of super knock conditions
occurring. Selective deployment of the super knock countermeasures
allow for the internal combustion engine 100 to operate at targeted
fuel consumption and power delivery levels when deployment of the
super knock countermeasures are not needed.
[0035] In one embodiment, the super knock countermeasure includes
advancing spark timing to discharge the spark plug 118 prior to the
piston 120 reaching top dead center. In such an embodiment, the
spark plug 118 may be discharged as soon as pre-ignition of the
air-fuel mixture is detected, so that a flame front that expands
through the air-fuel mixture from the spark plug 118 expands prior
to the piston 120 reaching top dead center. In some embodiments,
the discharge of the spark plug 118 may be set to a set point at
which all of the air-fuel mixture may be ignited and/or burned
prior to the piston 120 reaching top dead center. The advance of
the discharge of the spark plug 118 will reduce power output of the
internal combustion engine 100 for the detected and, thus, advanced
cycle. The correction may be deployed to a single engine cylinder,
and therefore may not greatly reduce total engine power. In some
embodiments, advancing the timing of the discharge of the spark
plug 118 may introduce conventional engine knock into the internal
combustion engine 100, because the heating and the pressure
increase of the air-fuel mixture in the combustion chamber 122 may
cause unburned portions of the air-fuel mixture to auto ignite.
However, the advance in timing of the discharge of the spark plug
118 may interrupt the continuation of conditions that lead to super
knock conditions forming in the combustion chamber 122.
[0036] Early ignition of the air-fuel mixture will lead to an
increase in pressure in the combustion chamber 122 prior to the
piston 120 reaching top dead center. This pressure will reduce
engine power for the selected cycle of the selected engine cylinder
110, and will increase fuel consumption of the internal combustion
engine 100 over cycles in which the super knock countermeasure is
deployed. Advancing the timing of the discharge of the spark plug
118 will reduce the power delivered by the internal combustion
engine 100 and will increase the fuel consumption of the internal
combustion engine 100, but will reduce the maximum pressures
experienced by components of the internal combustion engine 100 as
compared to those experienced in super knock conditions, thereby
protecting those components from damage caused by super knock
conditions. Because the high pressures experienced by engine
components during super knock conditions can damage engine
components, pressures associated with the super knock
countermeasures, including pressures associated with conventional
engine knock, are preferred.
[0037] Referring again to FIG. 2, in one embodiment, the internal
combustion engine 100 may include a second spark plug 124 that is
positioned to ignite air-fuel mixture that is present in the
combustion chamber 122. The second spark plug 124 may be configured
to be discharged only upon detection of formation of super knock
conditions by the engine control module 80. In some embodiments,
the ignition system 119 may not have sufficient charge built up
early in the compression stroke to discharge the spark plug 118 to
ignite the air-fuel mixture. In such cases, the ignition system 119
may hold a charge for the second spark plug 124 early in the
compression cycle for the designated combustion chamber 122.
Therefore, when pre-ignition of the air-fuel mixture is detected,
the second spark plug 124 has sufficient charge to ignite the
air-fuel mixture and initiate an early flame front through the
combustion chamber 122.
[0038] In one embodiment, the super knock countermeasure includes
exhausting of the air-fuel mixture and burned portions of the
air-fuel mixture during the compression stroke in which
pre-ignition of the air-fuel mixture is detected. Some embodiments
of the internal combustion engine 100 may include an exhaust valve
174 that has a hydraulic or an electronic lift mechanism 175. The
lift mechanism 175 is in electronic communication with the engine
control module 80. Under normal operation, the lift mechanism 175
selectively opens and closes the exhaust valve 174 according to a
predetermined schedule to selectively vent and seal, respectively,
the combustion chamber 122 at the exhaust port 173. When the engine
control module 80 determines that pre-ignition of the air-fuel
mixture has occurred in a compression stroke, the engine control
module 80 may deploy a super knock countermeasure of commanding the
lift mechanism 175 to open the exhaust valve 174 during the
detected compression stroke to reduce the pressure in the
combustion chamber 122 and to pass unburned and burned air-fuel
mixture from within the combustion chamber 122 to outside of the
combustion chamber 122. In such conditions, the engine control
module 80 may also interrupt the spark plug 118 from discharging
during the detected compression cycle. Opening the exhaust valve
174 with the lift mechanism 175 during the detected compression
stroke may interrupt the conditions leading to formation of super
knock conditions in the combustion chamber 122. For example, the
contents of the combustion chamber 122 may be vented by activation
of the lift mechanism.
[0039] In yet another embodiment, the super knock countermeasure
includes an additional injection of fuel into the combustion
chamber 122 to cool the air-fuel mixture that is present in the
combustion chamber 122, to enrich the air-fuel mixture to reduce
the likelihood of continued formation of super-knock conditions,
and to quench any flame front that has formed in the combustion
chamber 122 due to pre-ignition of the air-fuel mixture. In such
embodiments, when the engine control module 80 senses that
pre-ignition of the air-fuel mixture has occurred during the
compression stroke, the engine control module 80 may direct the
fuel injector 116 to inject fuel into the combustion chamber 122
during the detected compression stroke. By injecting the additional
fuel in the detected compression stroke, the additional fuel can
cool the air-fuel mixture, thereby stopping or delaying further
combustion of the air-fuel mixture caused by pre-ignition.
Accordingly, the injection of additional fuel may interrupt super
knock conditions from forming in the combustion chamber 122.
[0040] In some embodiments, the super knock countermeasures may be
selected to be deployed at engine conditions at which super knock
conditions could or are likely to occur. For example, super knock
conditions are likely to occur at low speed high power engine
conditions corresponding to throttle tip in. Because super knock
conditions have a lower likelihood of occurring at other engine
conditions, including at idle and when operating at wide open
throttle at or near maximum engine speed, deploying the super knock
countermeasures may cause undesired effects, such as undesired
engine knock, reduced power, or an increase in fuel
consumption.
[0041] The engine control module 80 may include a super knock
countermeasure schedule that corresponds to engine conditions at
which super knock conditions are possible or likely to occur. When
the engine operates within these conditions, the engine control
module 80 is selected to deploy the super knock countermeasures
when pre-ignition of the air-fuel mixture is detected. When the
engine operates outside of these conditions, the engine control
module 80 is locked out from deploying the super knock
countermeasures. Because super knock conditions are unlikely to
form at such engine conditions, the engine control module 80 does
not need to deploy the countermeasures to maintain healthy engine
operation. Accordingly, by electing to not deploy the super knock
countermeasures at engine conditions at which there is a low
likelihood of super knock conditions occurring, engine power and
fuel economy can be maintained by maintaining spark timing and
maintaining an air-fuel ratio near a stoichiometric ratio with
little concern of super knock conditions forming in the engine.
[0042] It should now be understood that internal combustion engines
according to the present disclosure include elements that detect
pre-ignition of an air-fuel mixture that is present in the
combustion chamber of the engine during an intake or compression
stroke. When the engine is operating under conditions corresponding
to formation of super knock conditions, the engine control module
may deploy super knock countermeasures to interrupt the formation
of super knock conditions in the detected compression stroke.
Deploying the super knock countermeasures may result in an increase
in pressure conditions in the combustion chamber, but reduce the
pressure conditions in the combustion chamber as compared to when
super knock conditions are permitted to fully develop. Interrupting
the full development of super knock conditions within the
combustion chamber may ensure engine health and may stop premature
engine failure due to super knock.
[0043] It will be apparent to those skilled in the art that various
modifications and variations can be made to the embodiments
described herein without departing from the spirit and scope of the
claimed subject matter. Thus it is intended that the specification
cover the modifications and variations of the various embodiments
described herein provided such modification and variations come
within the scope of the appended claims and their equivalents. It
is noted that the various details described in this disclosure
should not be taken to imply that these details relate to elements
that are essential components of the various embodiments described
in this disclosure, even in cases where a particular element is
illustrated in each of the drawings that accompany the present
description. Rather, the claims appended hereto should be taken as
the sole representation of the breadth of the present disclosure
and the corresponding scope of the various embodiments described in
this disclosure.
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